1. Field of Invention
The present invention relates to a low-k, flame-retardant, bi-functional benzoxazine and, more particularly, to a thermo-stable, flame-retardant, low-k, phosphoric, bi-functional benzoxazine and, more particularly, to a phosphoric benzoxazine with phosphor-oxide bonds made by synthesis of phosphoric diamine.
2. Related Prior Art
Phenolic resin is a common thermosetting resin made by condensation of a phenol monomer and an aldehyde monomer. Benzoxazine is a phenolic resin. By nature, benzoxazine is subjected to ring-opening and curing after it is heated. In comparison with a conventional phenolic resin, benzoxazine exhibits a high glass transition temperature (Tg), a high modulus, low moisture absorption, excellent electric properties, a high char yield, and does not require any catalyst of strong acid, produce any byproducts, or vary in volume during the curing.
Phenolic resin, which is composed of carbon, hydrogen and oxygen, is however easily combustible in use. As the electronic industry develops, electronic products get smaller and lighter. Hence, the pin through hole technology (“PTH”) has been replaced with the surface mount technology (“SMT”) such as the ball grid array (“BGA”), the flip chip package (“FCP”) and the chip size package (“CSP”). Printed circuit boards develop toward high-density and lamination. Moreover, the semiconductor industry gets more and more demanding on the temperature resistance and combustion resistance of materials. For example, all electronic materials must be in compliance with the regulations of UL-94 V-0. There is a trend to pursue flame-retardant electronic materials.
A currently available, flame-retardant benzoxazine includes carbon fibers added therein to improve the combustion resistance. It is however hard to make a flame-retardant, pure benzoxazine, and many efforts have been made to render a polymer flame-retardant. The flame-retardant property of a polymer can be improved by adding alkyen, deoxybenzoin or a phosphoric material therein.
It can be learned from many papers that most bi-functional benzoxazines are made of aromatic bi-sphenol, mono-functional amine monomer and methanol. A benzoxazine made of aromatic bi-sphenol however exhibits poor thermo-stability because its chemical bonds can easily be broken to release aniline at high temperature.
Moreover, it can be learned from many papers that a material of the structure of adamantane exhibits excellent mechanical properties and rigidity for two reasons. Firstly, it exhibits hardness and rigidity. Secondly, it exhibits a low polarity to dilute the influences from the polar structure of a curing material, and this is good for reducing the dielectric constant. It however mainly consists of aliphatic materials and is not flame-retardant.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.